(1) Field of the Invention
The present invention relates to an improvement in a cutting machine, in which two to four rotary blades are arranged around a cut material in a positionally variable manner, and further, the rotary blades are revolved along the outer periphery of the cut material at the same time and, more particularly, to a cutting machine, in which a square type tube having a square or rectangular cross section (hereinafter referred to as a square tube) in addition to a round type tube (hereinafter referred to as a round tube) can be cut within wide ranges of a size and a thickness at a high cutting speed or with a long lifetime of the rotary blade.
(2) Description of Related Art
A method for cutting a round tube or a square tube is exemplified by a method for moving a rotary blade or band saw having a large diameter in one diameter direction of a tube, and then, cutting the tube (hereinafter referred to as an R method). Alternatively, a method for cutting a round tube is exemplified by a method for revolving a rotating rotary blade on the tube, and then, cutting the tube. Specifically, there is a method for disposing one to three rotary blades in a doughnut-like face plate so as to rotate the face plate on the tube (hereinafter referred to as a θ method).
In the θ method, in which the face plate is rotated, a tube having a different diameter or a square tube cannot be cut. Therefore, a plurality of swing cutters, each including a swing arm having the rotary blade attached to the tip thereof and pivotally disposed in the face plate at the base end thereof, are disposed in the face plate, and then, the rotary blade is positionally controlled at a swing angle of each of the arms and a revolutionary angle of the face plate, so as to cut the tube (hereinafter referred to as a θ-θ method). (Japanese Patent No. 2939409 and Japanese Patent Application Publication No. Sho 62-27926)
In the same manner, another method for cutting a tube having a different diameter or a square tube is exemplified by a method for disposing, in a doughnut-like face plate, rotary blades disposed opposite to each other in a tube diameter direction in a positionally adjustable manner in a diameter direction, and then, rotating the face plate on the tube (hereinafter referred to as an R-θ method).
(Japanese Patent Application Laid-open No. Hei 09-47914)
A machine adopting the above-described θ-θ method requires a complicated machine mechanism for rotating rotary rings for inner circumferential teeth and outer peripheral teeth and numerous gears in a coaxially overlapping manner in order to rotate a saw blade; and a machine mechanism adapted to rotate the face plate for pivotally supporting a cutter head in order to adjust the swing of the cutter head or the position of a cut material in an outer peripheral direction. As the machine becomes larger in size, it is necessary to rotate a considerably heavy article and mechanically control its position. As a consequence, there rise the problems that the machine mechanism is complicated in the machine, mechanical processing for a large-diameter gear having a complicated curve or the like is cumbersome in fabricating, and further, maintenance during operation is not easy.
On the other hand, the R-θ method has experienced the following problems. Specifically, it is necessary to provide a rotary blade unit including a drive motor, a gear box, and a rotary blade in a movable manner in a radial direction of the face plate together with its drive source and a machine mechanism for rotating the face plate per se having the rotary blade unit provided therein. As the machine becomes larger in size, it is necessary to rotate a considerably heavy article and control it. Moreover, a traveling cutter need be constituted so as to move the above-described cutting machine at the same speed as that of the cut material, and further, much power is required for rotating the face plate having the heavy article and driving a traveling vehicle mounting them thereon.